The government attempted to head off a Labour rebellion against plans for a third runway at Heathrow yesterday, with rebel MPs, including a ministerial aide and a vice-chair of the Labour party, attending talks with Gordon Brown in Downing Street.

A consultation will report in the next few weeks on whether government plans for a new runway - built by 2020 and which would increase the number of flights from 480,000 a year to more than 700,000 - should go ahead. If the consultation is favourable, the government will push forward plans for the runway, which could put it on a collision course with backbenchers and cabinet ministers in the parliamentary year before a general election. Labour MPs in marginal seats whose constituencies will be affected by the plans have stepped up opposition in recent weeks.

Yesterday's delegation was led by Andrew Slaughter, parliamentary private secretary to the Foreign Office minister Mark Malloch-Brown, and Martin Salter, vice-chair of the Labour party. Fifty Labour backbenchers and 90 MPs from other parties have signed an early day motion, with leader of the Commons Harriet Harman, climate change secretary Ed Miliband and environment secretary Hilary Benn all thought to have voiced concerns about the expansion.

Presenting the government's case to the Commons, the transport secretary, Geoff Hoon, dismissed opposition claims that the government had already made up its mind and that the consultation was a sham. Hoon said 70% of foreign companies moving to the UK chose a location within an hour's drive of Heathrow. He said the aviation industry was responsible for 200,000 jobs in the UK, and was worth £11bn annually.

The shadow transport secretary, Theresa Villiers, said the environmental costs of the government's plans outweighed the economic benefits of expansion and claimed the government was "deaf to the concerns of people about the environment".

Villiers also said expanding Heathrow would endanger the government's 2050 goal of cutting carbon dioxide emissions by 80%. Labour backbencher David Taylor said proposals for airport expansion, which include a second runway at Stansted in Essex, had not factored in the impact of climate change and the disruption to nearby communities.

Fiona Mactaggart, Labour MP for Slough, said her constituents had been assured that there would be no further runways at Heathrow when planning permission was given for Terminal 5.

One rebel at the talks with the prime minister said he was "pessimistic" that they would gain any concessions from the government, but another involved in coordinating opposition to the plans said the tone struck by Hoon was more emollient than in previous weeks.